Railway signaling system



H. A. THOMPSON 2,357,236

,RAILWAY SIGNALING SYSTEM Aug. 29, 1944.

Filed March 26, 1942 Eig. l.

IZDZ/ NVENTOR. HowafdA/J/Qompfon H/STTUH/VEK Patente-d Aug. 29, i944 RAILWAY SIGNALING SYSTEM Howard A. Thompson, Edgewood, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of rPennsylvania Application March 26, 1942, Serial No. 436,327 4 14 Claims.

` fective joints to thereby prevent the display of a proceed indication by the signal for the section in advance of the defective joints, or by the cab signal Aapparatus on a locomotive in the section in the rear of the defective joints.

In the system shown in the patent identiiied above the steady energy supplied to the section in the rear of the defective joints causes the signal for that section to display its stop indicai tion, while it also causes steady uncoded energy to be suzpplied to the track sections farther in the rear so that all of the signals in `the rear of the defective insulated joints display stop indications, while the cab signal apparatus on a locomotive present in any of these sections will provide its most restrictive indication. This createsV a safe condition, but it may unnecessarily delay traflic in the track stretch.

In United States Patent No. 2,215,904, issued September 24, 1940, to Ralph R. Kemmerer, and

in' United states Patent No. 2,235,134, issued March 18, 1941, to Leslie R. Allison and Frank H. Nicholson, there are shown non-cascading lockout circuit in which the supply of steady energy is not repeated beyond the section in thefrear of the defective insulated joints. tems the signal at the defective insulated joints, and the adjacent section in the rear display stop indications, but the signals farther in the rear display proceed indications. This arrangement facilitates Ymovement of traiiic, but it still requires trains to' traverse two track sections at slow speed.

It is an object of this invention to Iprovide an improved system of the type describedwhich operates so that in the event that'the insulated vjoints separating two track sectionsV are defective fective joint, and which operates so that afterl this energy has been vdetected the equipment In these sys- Y cannot be restored to normal operation byk any track lcircuit conditions, but can only be returned to normal operation by action of a signal maintainer. f

Other objects of the invention and features of novelty will be apparent from the following description taken in connection with the accompanying drawing.

In practicing my invention I modify the systems heretofore known by incorporating in the equipment for each track section a relay which is .controlled in such manner as to detect the steadily energized condition of the associated track relay, and I employ this relay to control the suply of steady energy to the section in the rear. Should the normally coded energy supplied to one track circuit feed forwardly across a defective joint so that the lockout circuit becomes effective to supply steady energy to the rear, the relay added by this invention will detect the presence of this steady energy and will Ycut off the further supply of steady energy to the rear section and will cause coded energy to be supplied instead. VIn addition, when the system includes wayside signals the relay added by may invention also operates after it has detected the presence of steady. energy to maintain the display of the most restrictive indication by the associatedsignal.

I shall describe one form of signaling system embodying my invention together with two modiiications thereof which I may employ, and shall then point out the novel features thereof in "claimsl In the drawing Fig. 1 is a diagram showing a section of railway track equipped with signaling apparatus embodying my invention, and f Figs. 2 'and 3 are fragmentary diagrams showing modifications which I may employ.

Similar reference characters refer to similar parts in each of the three views. l

Referring to Fig. 1, there is shown therein a stretch` of Arailway trackhaving track rails l and 2 over which traffic normally movesin the direction indicated byan arrow, that is, from 'aleft'to right. The rails of the track stretch are divided by insulated joints 3 into the Icustomary the apparatus of this invention is equally -well suited for use on a steam road, in whichcavse either direct or alternating current may be employed in the track .circuits while the impedance bonds may be omitted.

Inv the diagram comprising Fig. 1 of the drawing one complete section, which is identified as section I2T, and parts of two other sections, identied as sections I IT and I3T, are shown. Each of these sections has located at the entrance end thereof a signal S for governing trafc in the track stretch. The signals illustrated are of the familiar color light type having a green or proceed lamp G, a yellow or caution lamp Y, and a red lamp R which may be considered a stop or slow speed indication. It should be understood, however, that the invention is not limited to the use of signals of this type and that any appropriate form of signal may be used. Likewise, the invention is not limited to a system employing wayside signals. but is equally applicable to track stretches without wayside signals and over which are operated locomotives equipped with cab signal apparatus of well known construction, such as that shown in United States Patent No. 1,986,679, issued January l, 1935, to Lloyd V. Lewis.

The rails of each track section form a part of a track circuit to which coded alternating current signal control energy is supplied at the exit or leaving end from the secondary winding of a track transformer TT. The alternating current supplied to the track circuits is derived from a suitable sour-ce and may be distributed throughout the track stretch by a transmission line, not shown. The terminals of the power supply source are designated BX and CX, and it will be assumed that the energy supplied from this source is alternating current of a frequency of 100 cycles per second.

Each signal location is also provided with a suitable source of direct current, such as a primary or storage battery, not shown, the terminals of which are designated B and C.

The signaling system shown in Fig. l makes use of track circuit energy coded at two different frequencies. This coded energy is provided by code transmitters CT which interrupt the supply circuits for the associated track transformers a definite number of times per minute according to traffic or other conditions ahead. As shown, each code transmitter is provided with two circuit making and breaking contacts 'I5 and |80 which are continuously actuated by a motor or other suitable mechanism at speeds such as to provide 75 and 180 energy pulses per minute which are separated by periods of equal duration in which no energy is supplied.

Each track circuit includes a code following track relay TR connected across the section rails at the entrance end of the section. As shown, the track relay is of the direct current type and is connected to the track rails through a resonant rectifier unit RU. The unit RU includes a transformer, a capacitor and a reactor so arranged and proportioned as to freely pass 100 cycle signal control energy, but so as not to pass propulsion current of a different frequency. The unit RU includes, in addition, a rectier which converts into direct current -the alternating current supplied through the unit. Y Y

The track relay IZTR has associated therewith auxiliary relays I2FSA, IZBSA, I2H and I2J, a slow releasing control relay IZLOS, and a decoding transformer I2DT, while each of the other signals in the track stretch has associated therewithl equipment corresponding to that associated with signal I 2S.

The equipment is shown in the condition which it assumes when the track stretch is vacant. At such times energy of 180` code frequency is supplied tothe track transformer I ZTT by the equip- -ment associated with section IST. The equipment for section I3T operates in the sa-me manner as that for section I2T.

The coded energy supplied to the transformer I 2TT feeds to the track relay IZTR and produces code following operation of this relay. When the track relay contacts are in their picked-up positions, contact I6 establishes a circuit to supply energy to the first auxiliary relay IZFSA, while during the released periods of the track relay contacts energy is supplied to second auxiliary relay IZBSA over the circuit which is traced from terminal B through back contact I6 of relay I2TR, front contact I'l of relay IZLOS, front contact I8 of relay IZFSA, and winding of relay I2BSA to terminal C. At thisv time contact I8 of relay IZFSA also connects the snubbing resistor 2D across the terminals of the relay IZBSA to render the relay slow in releasing so that the relay contacts remain picked up during the picked-up periods of the track relay contacts. Similarly, the relay IZFSA. is of a type the contacts of which are slow in releasing so that they remain picked up during the released periods of the track relay contacts.

As a result of code following operation cf the track relay its contact 2| .alternately establishes the circuits toenergize the two portions of the primary winding of transformer I2DI so that impulses of energy are supplied to the secondary windings 22 and -23 of the transformer.

When the track relay contacts are picked up, its contact 25 establishes a circuit including front contact 25 of relay IZBSA to supply impulses o'f energy from the transformer secondary winding 23 to the relay I2H. The relay H is of a type which is slow in releasing so that its contacts remain picked up during the intervals between the supply of impulses of energy to the relay winding.

As the contacts of relays IZFSA and IZBSA are picked up, energy is supplied to the control relay I2LOS over the circuit which includes front contact 28 of relay IZFSA and front contact 29 of relay I2BSA.

As the contacts of relays IZFSA, IZBSA and I2H are picked up, energy of 180 code frequency is supplied to the primary winding of track transformer IIT'I over the circuit which is traced from terminal BX through contact of the code transmitter IZCT, front contact 30 of relay I2H, front contact 3l of relay I2BSA, front contact 32 of relay I2FSA, and primary winding of transformer IITT to terminal CX. Accordingly, energy of code frequency is supplied to the rails of section I IT.

At this time energy induced in the secondary winding 22 of transformer I2DT is supplied through the resonant rectifier unit I2DU to the relay I2J so that the Contact of this relay is picked up. Accordingly, the green lamp G of signalV I2S is'lighted over the circuit which includes front contact 34 of relay I2H and front contact A35 of relay 'I 2J.

The unit I2DU is similar in construction to the unit I2RU, but is arranged to pass sufficient energy to pick up the relay I 2J when and only when the energy supplied thereto is of the frequency present when the track relay I2TR is lresponding to energy of 180 code frequency.

When a train moving in the normal 'direction of traffic enters section IZT, the track relay IZTR is shunted and its contacts remain in their released positions so that energy is not supplied to the relays IZFSA and IZI-I. Accordingly, after a short time interval the contacts of relay IZFSA release so that its contact I8 interrupts both the energizing circuit and the 'snubbing circuit for relay IZBSA, and the contacts of this relay thereupon quickly release so that contact 2B interrupts the circuit of relay I2H and its contacts' release after a time interval.

On release of the contacts of relay IZFSA contact 28 interrupts the circuit o-f relay I2LOS, but this relay is slow enoughin releasing to remain picked up until contact 29 of relay I2BSA re,- leases and establishes the circuit of the relay IZLOS. Accordingly, the contacts of relay IZLOS remain picked up and energy of '75 code frequency is supplied to the track transformer I ITT over the circuit. which is traced from terminal BX through front contact 3l of relay IZLOS, back Contact 3l of relay I ZBSA, back contact 32 of relay I2FSA, contact 'I5 of the code transmitter, and primary winding of the track transformer I ITT to lterminal CX.

As hereinafter explained in connection with section I2T, the energy of 75 code frequency supplied to section l IT will cause the signal for that section to display its yellow or caution indication, while it will produce a similar aspect in the cab signal apparatus on a locomotive in section IIT.

On release of the contacts of relay IZH contact 34 interrupts the circuit of the green lamp VGr of signal IZS and establishes the circuit of the red lamp R, while on cessation of code following operation of the track relay I2TR relay I2J releases. A

When the train enters section I3T, the equip'- ment for this section operates in the same manner as that associated with section I2T so that the signal ISS displays its red indication, while the energy supplied to track transformer I2TT is changed from 180 to 75 code frequency.

` When the train vacates section IZT, the energy of '75 code frequency feeds to the track relay IZTR and produces code following operation oi the relay.

On picking up of the track relay contacts its contact It establishes the circuit to supply energy to relay IZFSA and the contacts of this relay pick up so that contact 32 interrupts the circuit traced alooVe for supplying energy of '75 code frequency to the transformer IITT, Vand establishes the circuit including front contact v3'! of relay IZLOS and back contact 3I of relay IZBSA to supply steady uncoded energy to transformer IITT.V If the insulated joints 3 separating sections IIT and and IZT are intact, the steady energy supplied totrack transformer l ITT will not reach track relay I2TR, and this relay will continue to respond to the coded energy supplied thereto from transformer I2TT.

After a short time interval, therefore, the track relay contacts will release and contact I6 establishes the circuit including front contact I1 of relay IZLOS and front contact I8 of relay IZFSAl for energizing relay I2BSA. The contacts of relay IZBSA, therefore, pick up and its oontact 26 is closed so that on the next movement of the track relay contacts to their picked-up positions energy is supplied to relay IZH, while4 contact 3| of 'relay IZBSA interrupts the circuit traced above for supplying steady energy to track transformer IITT.

In addition, on picking up of the contacts of relay IZBSA its contact 29 establishes thecircuit including front contact 28 of relay IZFSA for supplying energy to the relay IZLO'S. In the interval between picking up of the contacts of relay IZFSA and picking up of the contacts of relay IZBSA energy is not supplied to the relay IZLOS, but this relay is slow enough in releasing to keep its contacts picked up during this time interval.

When the track relay contacts again pick up, energy is supplied to relay IZFSA to keep it picked up, While energy is supplied to relay IZH to pick up its contacts. On picking upv of the contacts of relay IZH its Contact 30 completes the circuit*l for supplying energy of code frequency to track transformer IITT, while its contact 36 interrupts the circuit of the red lamp R and establishes the circuit including back contact 35 of relay I2J for lighting the yellow lamp Y of signal I2S. The energy of 180 code frequency supplied to the rails of section I IT causes the signal for that section to display its green or clear indication, while it will cause the display of a similar indication by the cab signal apparatus on a locomotive present in this section.

On continued code following operation of the track relay energy is supplied to the relays IZFSA and IZI-I on movement of the track relay contacts to their picked-up positions, while energy is supplied to the relay IZBSA on movement of the track relay contacts to their released po sitions. Accordingly, as long as the track relay responds to coded energy, the contacts of the relays I ZFSA, IZBSA and I 2H are picked up, while contact 28 of relay IZFSA and contact 29 of relay IZBSA establish the circuit of the relay IZLOS so that its contacts are maintained picked At this time, as the track relay I2'1R is responding to energy of '75 code frequency, the frequency. of the energy induced in the secondary winding 22 of decoding transformer IEDT is such that too little energy is supplied through the unit IZDU to the relay I2J to pick up the relay contact so that its contact 35 remains released and maintains the circuit of the yellow or cau tion lamp Y of signal I2S. v

When the train advances far enough to vacate section IST, the equipment associated with this section operates to change the aspect of signal I3S from red to yellow, and to` change vthe energy supplied to track transformer I ZTT from 75 to 180 code frequency. Accordingly, the track relay IZTR operates at a faster rate and relays IZFSA, I2BSA and IZH are maintained energized, while suflicient energy is supplied through the unit IZDU to the relay I2J to pick up the vrelay contact so that its contact 35 .picks up and interrupts .the circuit of the yellow lamp Y and establishes the circuit of the green lamp G of signal I2S. At this time energy of 180 co-de frequency continues to be supplied to the track transformer Il TT.

Operation of the equipment if an insulated joint breaks down as a resutt of passage of a train When a train moving in the normal direction of trallic enters section I 2T, the track relay IZTR is shunted and relays szrsA, :zBsA and 2H release as explained above, while energy;is supplied to relay IZLOS over the circuit established by back contacts 28 and 29 of relays IZFSA and IZBSA. Accordingly, the circuit including front contact 31 of relay I 2LOS, back contact 3l of relay IZBSA, back contact 32 of relay IZFSA, and contact 15 of the code transmitter I2CT is established to supply coded energy to the transformer I ITT.

For purposes of illustration it will be assumed that an insulated joint 3 separating sections I IT and IZT breaks down as a result of passage of a train. Because of the Well-known autotransformer action of the impedance bonds, breaking down of one insulated joint permits energy supplied to the rails of section IIT to feed to the track relay IZTR.

Accordingly, When the train advances far enough for the rear of the train to be located some distance in advance of the entrance end of the track section I2T so that the train is ineffective to shunt the track relay I2TR With respect to energy feeding across the defective joint, the track relay I ZTR. will respond to energy supplied from transformer I ITT.

On the first movement of the track relay contacts to their picked-up positions contact I6 establishes the circuit to supply energy to the relay IZFSA, and the contacts of this relay pick up so that its contact 32 interrupts the circuit traced above for supplying energy of 75 code frequency to track transformer IITT and establishes the circuit including front contact 31 of relay I 2LOS and back contact 3l of relay IZBSA for supplying steady energy to the transformer I ITT. This steady energy feeds across the defective joint to the track relay IZTRl and keeps the contacts of this relay in their picked-up positions so that contact I6 maintains the supply of energy to relay I2FSA, and does not engage Vits back contact to establish the circuit to supply energy to the relay IZBSA. Accordingly, the contacts of relay IZBSA remain released.

When the contacts of relay IZFSA are picked up and the contacts of relay IZBSA are released, the circuit of the relay I2LOS is interrupted, and

'after a short time interval, the contacts of this relay release so that its contact 31 interrupts the circuit traced above for supplying steady energy to the track transformer IITT and establishes a circuit including contact 15 of the code transmitter to supply energy of 75 code frequency to the track transformer IITT. In addition, on release of the contacts of relay IZLOS its contact I1 interrupts the circuit of relay I2BSA to prevent energization of this relay.

The coded energy supplied to track transformer IITT feeds to the track relay IZ'I'R and the contacts of this relay now follow code. However, on release of the track relay contacts energy is not supplied to relay I2BSA since the circuit of this relay is interrupted by contact I1 of relay IZLO'S and relay IZBSA remains released so that its contact 26 interrupts the circuit of the relay I2H to thereby prevent the supply of energy to relay IZH on movement of the track relay contacts to their picked-up positions. Accordingly, on continued code following operation of the track relay I2TR subsequent to release of relay IZLOS energy is supplied to relay IZFSA on movement of the track relay contacts to` their pickedup positions, While energy is not supplied to relays IZBSA and I2H so that relay I2BSA remains released and continues to interrupt the circuit of relay IZLOS, while relay I2H remains released and its contact 34 maintains the circuit of the red lamp R of signal I2S.

It will be seen, therefore, that this system is arranged so that on initial picking up of the track relay contacts steady energy is supplied to the section in the rear, and, if this steady energy feeds across a defective joint, it will keep the track relay picked up so that the relay LOS releases and cuts oif the supply of steady energy to the section in the rear and causes coded energy of 75 code frequency to be supplied thereto. As hereinafter explained this energy of 75 code frequency supplied to section IIT causes the signal for that section to provide its caution indication, While it will produce a similar indication by the cab signal apparatus on a locomotive present in that section. In addition, release of relay IZLOS prevents completion of the cycle of picking up of the auxiliary relays and thereby insures that the signal I2S controlled thereby will continue to display its stop indication.

This system is also arranged so that the equipment associated with the track section in the rear of a defective insulated joint will display its yellow or caution indication.

For the purposes of illustration it will be assumed that an insulated joint 3 separating sections I2T and I 3T breaks down as a result of passage of a train and that the equipment for section I3T operates as described in detail above in connection with section I2T to detect the defective condition of the insulated joints.

As explained above, when any part of the train is present in section I2T, current from the track transformer I2TT is shunted from the track relay IZTR, While when the train enters section I3T, the track relay for that section is shunted and the equipment controlled thereby operates to supply energy of 75 code frequency to the track transformer I2TT.

When the train vacates section I 2T, the energy of 15 code frequency supplied to transformer I2TT feeds to the track relay IZTR and the first impulse of coded energy picks up the contacts of this relay so that its contact I6 establishes the circuit of the relay IZFSA, while on the rst olf period in the code the track relay contacts release so that energy is supplied to relay IZBSA and contact 29 of this relay picks up and reestablishes the circuit of the relay IZLOS,v

When the train advances far enough for the rear of the train to be located some distance in advance of the entrance end of section I3T, the train is no longer effective to shunt the track relay for section I3T with respect to energy feeding from the track transformer IZTT across the defective joint. v v

On the first movement of the contacts of the track relay for section I3T to their picked-up position energy is supplied to the relay IBFSA, not shown, and its contacts pick up to cut off the supply of coded energy to transformer I2TT and to cause steady energy to be supplied thereto. In addition, on picking up of the contacts of relay I3FSA the circuit of relay I3LOS is interrupted and the release time of this relay begins.

The steady energy supplied to the transformer I2TT causes lthe contacts of track relays I2TR and I3TR to remain picked up and maintain the circuits of the associated relays FSA.

After a time interval the relay I3LOS releases and cuts off the supply of steady energy to transformer I2TT and causes coded energy to be supplied thereto, While it also interrupts the circuit of relay I3BSA `to prevent energization of this relay on subsequent code following operation of the track relay I 3TR. y

On the supply of steady energy to relay IZTR its contacts remain picked up so that energy is not supplied to relay IZBSA and this relay releases after a time interval. This period is relatively long as the snubbing circuit for the relay is maintained by contact I8 of relay IZFSA.v Until relay IZBSA releases energy is supplied to relay IZLOS so that the release period of this relay IZLOS does not begin until after release of relay I2BSA. As pointed out above, the release period of relay ISLOS begins as soon as relay I3FSA picks up. As a result, the relay IZLOS will remain pickedup and will maintain the circuit of the relay IZBSA until after the relay I3LOS releases and causes coded energy to be supplied to transformer IZTT. Accordingly, on the first off interval in the coded energy supplied after release of the conf tacts of relay I3LOS, the contacts of relay I2TR release and energy is supplied to relay I2BSA to pick up the relay contacts if they have released, or to maintain them picked up if they have not released. The contacts of relay IZBSA, therefore, either maintain the circuit of relay IZLOSor reestablish it before it has been interrupted long enough for the relay I2LOS to have become freleased and interrupt the circuit of the relay |2BsA.

On continued supply of coded energy to the relay IZTR, therefore, on movement of the ltrack relay contacts to their picked-up positions en ergy is supplied to relay I2FS|A and is also supplied from the transformer I2DT to relay I2H, while on movement of the track contacts to their released positions energy is supplied to relay IZBSA.l Y

As relays IFSA, I2BSA and I2H are picked up, energy of 180 code frequency is supplied to transformer IITT, while as relay I2H is-picked up,

its contact 34 establishes thecircuit of the yellow lamp Y of signal IZS. Y

On the supply of coded energy to relay I3TR subsequent to release of relay IBLOS this track relay follows code and during the picked-up periods of its contacts energy is supplied to the relay ISFSA, but .during the released periods of the track relay energy is not supplied to relay ISBSA as the circuit of this relay is interrupted by'relay I3LOS. Accordingly, relay I3BSA will interrupt the circuit of relay ISH and this relay will maintain the circuit of the red lamp of signal ISS.

From the foregoing it will be seen that when an insulated joint separating two sections breaks down as a result of passage of a train, this system operates' to supply steady energy to the section in the rear to test the joints, but `after a short period the supply of steady energy is out off and coded energy is again supplied, and this coded energy causes the display of a yellow or caution indication by the signal for the section in the rear of the defective joints, or by thecab signal apparatus on a locomotive present in that section. Y ,Y Cperatzon of equipment if an insulated joint breaks down 'when the track stretch is vacant For purposes of illustration it will be assumed that one of the joints separating sections IIT and I2T breaks down at a, time when the track stretch is vacant. As the stretch is assumed to be vacant,

energy of 180 code frequency is suppliedto transsections IIT and I2T breaks down the'impulses of energy supplied to section IIT are out of step with those supplied'to section IZT, the impulses of energy supplied to section IIT and feeding over the defective insulated joint to track relay I2TR will ll in the off periods in the code supplied to section I2 T so that the track relay IZTR will be maintained picked up all, or substantially all, of the time.

If at the time the insulated joint becomes defective the impulses of code supplied to the two sections are substantially in step with each other, they will soon become out of step. This will be true because the code transmitters which create the code for the two sections are driven by electric motors of the squirrel cage induction type, and these motors will n ot operate at exactly the same speed for any substantial period of time. Accordingly, if track relay IZTR is not held picked up an abnormally large proportion of the time immediately upon breaking down of the joint, the track relay will soon be held up an abnormally large proportion of the time because of the increase in the time during which-energy is supplied tothe track relay when the two codes get out of step. In consequence of the lengthened picked-up periods of track relay IZTR Contact I6 will not engage tis back contact, or will engage it for such short time intervals that energization of relay IZBSA is reduced below the value effective to maintain the relay picked up. As the track relay is maintained picked up most of the time, energy is supplied to therelay IZFSA to maintain it picked up. v On release of relay IZBSA its contact 3| interrupts the lcircuit for supplying energy of 180 code frequency to the transformer IITT and establishes the circuit including front contact 3l of relay IZLOS, back contact 3| of relay IZBSA, and front contact 32'of relay IZFSA for supplying steady energy to transformer I ITT. In addition, on release of relay IZBSA its contact 29 interrupts the circuit of relay I2LOS and the release period of this relay begins.

Furthermore, on release of relay IZBSA its contact 26 interrupts' the kcircuit of relay I2H so that it releases and causes signal I2S to display its red indication.

The steady energy supplied to transformer II'IT feeds across the defective joint to relay IZTR so that this relay is maintained constantly picked up to thereby maintain the circuit of relay IZFSA and to prevent the supply of energy to relay IZBSA. After a short time interval relay IZLOS releases and interrupts the circuit of relay ZBSA, while it also cuts ci the supply of steady energy to section IIT and causes energy of 'I5 code frequency to be supplied thereto. This energy feeds across the defective joint to relay IZTR and combines with the energy of 180 code frequency supplied from transformer I2TT so that track relay IZTR. is maintained picked up most of the time and energy, therefore, `is supplied to relay yIQFSA to keep it picked up and thus keep relay IZLOS released. Even if the contacts of the track 'relay'release at times, energy `will not he supplied to relay IZBSA as the circuit of this relay is interrupted'by contact I'l of relay IZLOS. Relay I2BSA, therefore, Ywill remain released and will prevent energization of If at the time the insulated joint separating relay I2H so that the signal I2S will continue to display its red indication.

On release of relay IZBSA and the supply of steady energy to section IIT the track relayv for this section is held picked up, but as explained above, the relay I ILOS associated therewith does not start to release until after relay HBSA releases, while therelease time of relay IIBSA does not start until after relay IZBSA releases and initiates the supply of steady energy to section Il T, and the relay IILOS is certain to remain picked up until after relay .|2LOS releases and causes coded energy to again be supplied to section IIT. This coded energy of I5 code frequency will cause the signal for section IIT to displayl its yellow or caution indication.

Restoring equipment to normal operation after a defective joint has been detected `The system of this invention is arranged so that after the equipment for a section detects the presence of a defective joint, the equipment cannot be restored to normal operation until the defective joint is repaired and the circuit of the relay FSA is interrupted by means provided for this purpose.

As previously explained, after a defective joint has been detected, relay FSA is energized while relays BSA and LOS are deenergized. As relay LOS in deenergized, it interrupts the circuit of relay BSA, and as relay BSA is deenergized and FSA is energized, the circuit of LOS is interrupted. Accordingly, as long as the track relay follows coded energy, relay FSA will be maintained picked up while relays BSA and LOS will remain released. This will be true even after the defective joint is repaired so that the track relay is no longer supplied with energy feeding across the defective joint.

In order to restore the equipment to normal operation the signal maintainer or Aother authorized person depresses the push button PB and thus interrupts the circuity of relay FSA so that it releases and its contact 28 establishes the circuit of relay LOS. RelayLOS thereupon picks up and establishes the circuit of relay BSA. After Vthe push button is released and restores the circuit of FSA, this relay picks up on the first movement of the track relay contacts to their picked-up position, while the equipment thereafter functions in the normal manner.

Modifications shown in Figs. .2 and 3 In the system shown in Fig. 1 after a defective joint has been detected, the relay FSA is energized by current supplied thereto when the track relay contacts are picked up. As long as the joint is defective and the section in advance of the joint is vacant, the track relay is supplied with energy from two sources, one of these sources being the track transformer for the section with which the track relay is associated, and the other source being the energy supplied over the defective joint. Accordingly, under normal conditions the track relay will be energized most of the time so that relay FSA will be energized most of the time, and the intervals during which the track relay contacts are released and interrupt the circuit of relay FSA are infrequent and are much shorter than the release time of relay FSA. This relay FSA, therefore, will remain picked up and interrupt the circuit of relay LOS.

However, where the alternating current for two adjoining track sections is supplied from two different sources, the frequency of this energy may be slightly different and the phase relationship of the two sources of energy may be such that the half cycle impulses of alternating current from the different sources substantially neutralize each other.

Under these conditions the track relay will release, but unless the track relay remains released for a substantial period, the system of Fig. l operates to prevent the display of a proceed indication by the signal for the section in advance of the defective joint, or a change in the energy supplied tothe section in the rear of the defective joint.

Under some conditions the track relay may remain released longer than the release period of relay FSA, and if this occurs relay FSA will release and establish the circuit of relay LOS. On the nextl movement of the track relay contacts to their pick-up positions relay FSA will pick up and cause steady energy to be supplied to the section in the rear to keep the track relay picked up until LOS releases and interrupts the circuit of BSA.

If the frequency relationship of the two sources is at a critical value, the periods'in which the two sources neutralize or offset each other, and the periods in which they supplement each other, may occur at intervals such that the lockout condition will be interrupted after it has been established, and the modification shown in Fig. 2 is arranged to eliminate this possibility.

Referring to Fig. 2, it will be seen that in this modification when the relay LOS releases, its contact 40 establishes a circuit to energize the relay FSA so that thereafter this relay is energized independently of the track relay contact, and the relay will remain energized regardless of whether or not the track relay remains picked up. As the relay FSA is maintained energized, it will interrupt the circuit of relay LOS so that relay LOS interrupts the circuit of relay BSA. It will be seen, therefore, that the modication shown in Fig. 2 operates to prevent interruption of the lockou condition once it has been established.

If desired, the circuit governed by contact 40 of relay LOS for supplying energy to relay FSA may include a front contact 4l of relay FSA to thereby prevent picking up of relay FSA in the event ofreleaserof LOS at a time when FSA is released. v

The modification shown in Fig. 2 is otherwise the same as that shown in Fig. 1 and a detailed description thereof is unnecessary.

In Fig. 3 of the drawing there is shown another means which I may employ to maintain the relay FSA energized after release of relay LOS to thereby prevent interruption of the lockout condition after it has been established. In this modification contact l1 of relay LOS when released establishes a circuit over which energy is supplied to the relay FSA when the track relay TR is released. Accordingly, after release of relay LOS the relay FSA is energized directly over track relay contact I6 during the picked-up periods of the track relay, while during the released periods of the track relay contacts relay FSA is energized over the circuit established by contact l 'l of relay LOS. The relay FSA, therefore, will remain picked up at all times and will maintain the lockou condition.

A front contact of the relay FSA may be in eluded in the circuit controlled by contact l1 of relay LOS for supplying energy to relay FSA to prevent energization of relay FSA on release of relay LOS when the contacts of relay FSA are released. Y

The modifications shown in Figs. 2 and 3 include the push button PB to effect release of the contacts of relay FSA after release of the contacts of relay LOS to thereby restore the equipment to its normal condition.

Although I have illustrated and described onlyone form of railway signaling system embodying my invention, together with two modifications thereof which I may employ, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is: 1

l. In a coded railway signaling system, in cornbination, a stretch f railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow releasing control relay, a, circuit including a back contact of said first auxiliary relay for supplying energy to said control relay, a circuit including a front contact of said second auxiliary relay for also supplying energy to the said control relay, a circuit including a front contact of the track relay for supplying energy to the rst auxiliary relay, a circuit including a back contact of the track relay and front contacts of said first auxiliary relay and of said control relay for supplying energy to the second auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of the rearward'section, a circuit including front contacts of said first auxiliary relay andof said control relay and a back contact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, and a circuit including front contacts of said rst and second auxiliary relays for supplying coded energy to the rails offsaid rearward section.

2. In a coded railway signaling system, in cornbination, a stretch of railwayv track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow releasing control relay, a circuit in cluding a back contact of said rlrst auxiliary relay for supplying energy to said control relay, a cricuit including a front Contact of said second `auxiliary relay for also supplying energy to said control relay, a circuit including a front contact of the track relay for supplying energy to the first auxiliary relay, acircuit including a back contact of the track relay and front contacts of said first auxiliary relay and of said control relay for supplying energy to the second auxiliary relay, a circuit including a back contact of one of the auxiliary relays for supplying coded energy to the rails ofthe rearward section, a circuit including front contacts of said rst auxiliary relay and said control relay Vand a back contact of the second auxiliary relay over which steady energy -may b-e supplied to the rails of said rearward section, a circuit including front contacts of said rst and second auxiliary relays for supplying coded energy to the rails of said rearward section,

and manually controlled means for interrupting the circuit of the rst auxiliary relay.

3. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails dividedI by insulated -joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy tothe rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first, :a second and a third auxiliary relay, a circuit including a back contact of the' first auxiliary relay for supplying energy to the third auxiliary relay, -a circuit including a front contact of the second auxiliary relay for also supplying energy to the third auxiliary relay, a circuit including a front contact of the track relay for supplying energy to the first auxiliary relay, a circuit including a back contact of 'the track relay and front contacts of the first and third auxiliary relays for supplying energy to the second auxiliary relay, a circuit including back contacts of the first and second auxiliary relays and a front contact of the third auxiliary relay for supplying coded energy to the rails of the rearward section, a circuit including front contacts of the first and third auxiliary relays and a back contact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, a circuit including front contacts of said rst and second auxiliary relays for supplying coded energy to the rails of said v'rearward section, a circuit including a back contact of said third auxiliary relay for also supplying coded energy to the rails of said rearward section, and manually operable means for governing the circuit of one of said auxiliary relays.

4. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track vrails divided by insulated joints into a plurality of successive track sections including a forward and arearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow releasing control relay, a circuit including a back contact of the said first auxiliary relay for supplying energy to said control relay, a circuit including a front contact of the second auxiliary relay for also supplying energy to said control relay, a circuit including a front contact of the track relay for supplying" energy to the first auxiliary relay, a circuit including a back contact of the track relay and front contacts of the first auxiliary relay and of said control relay for supplying energy to the second auxiliary relay, a circuit including. a back contact of one of said auxiliary relays for supplying coded energy of arst code frequency to the rails of said rearward section, a circuit including front contacts of the first auxiliary relay and of said control relay and a back contact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, and a circuit including front contacts oi the rst and second auxiliary relays for supplying coded energy of a second code frequency to the rails of said rearward section.

5. I n a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints inn to a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow releasing control relay, a circuit including a back contact of the first auxiliary relay for supplying energy to said control relay, a circuit including a front contact of the second auxiliary relay for also supplying energy to said control relay,- a circuit including a front contact of the track relay for supplying energy to the rst auxiliary relay, a circuit including a back contact of the track relay and front contacts of the first auxiliary relay and of said control relay for supplying energy to the second auxiliary relay, a circuit including a back contact of one of said auxiliary vrelays for supplying coded energy to the rails of the rearward section, a circuit including front contacts of the first auxiliary relay and of said control relay and a back contact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, a circuit including front contacts of said first and second auxiliary relays for supplying coded energy to the rails of said rearward section, a signal governing trailic in said forward section, and means responsive to continued code following operation of the track relay subsequent to picking up of the contacts of the second `auxiliary relay for controlling said signal.

6. In a a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first, a second and a third auxiliary relay, a circuit including a back contact of the first auxiliary relay for supplying energy to the third auxiliary relay, a circuit including a front contact of the second auxiliary relay for also supplying energy to the third auxiliary relay, a circuit including a front contact of the track relay for supplying energy to the first auxiliary relay, a circuit including a back contact of the track relay and front contacts of the rst and third auxiliary relays for supplying energy to the second auxiliary relay, a circuit including back contacts of the first and second auxiliary relays and a front contact of the third auxiliary relay for supplying coded energy of a firstl code frequency to the rails of said rearward section, a circuit including front contacts of the first and third auxiliary relays and a back con- Ytact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, a circuit including a back contact of said third auxiliary relay for supplying coded energy of said first code frequency to the rails of said rearward section, a fourth auxiliary relay, means responsive to continued code following operation of the track relay subsequent to picking up of the contacts of said seco-nd auxiliary relay for energizing said fourth auxiliary relay, a signal for said forward section controlled by said fourth auxiliary relay, and a circuit including a front contact of said fourth auxiliary relay for supplying coded energy of a second code frequency to the rails of said rearward section.

'7..EIn a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided .by insulated joints into a plurality ofsuccessive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a rst and a second auxiliary relay, a slow acting control relay having contacts movable between a rst and a second position, the circuit of said control relay being governed by said auxiliary relays in such manner that when the contacts of both of said relays are released the contacts of said control relay occupy their first position and so that When the contacts of the first relay are picked up while the contacts of the second auxiliary relay are released the contacts of said control relay move t0 their second position after a time interval, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a back contact of the track relay, a front contact of the rst auxiliary relay and a Contact of said control relay closed when the contacts Of said relay are in their first position for supplying energy to the winding of said second auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the rst auxiliary relay, Aa back contact of the second auxiliary relay, and a contact of said control relay which is closed when the contacts of said relay are in their rst position over which steady energy may be sup-plied to the rails of said rearward section, and means responsive to continued code following operation of the track relay subsequent to picking up ofqthe contacts of said first auxiliaryl relay for also supplying coded energy to the rails of said rearward section.

8. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into ar plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the vrails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a rst and a second auxiliary relay, a slow acting control relay having contacts movable between a first and a second position, the circuit of said control relay being governed by said auxiliary relays in such manner that when the contacts of both of said relays are released the contacts of said control relay occupy their first position and so that when the contacts of the first relay are vpicked up while the contacts of the second auxiliary relay are released the contacts of said control relay move to their second position after a time interval, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a back contact of the track relay, a front contact of the rst auxiliary relay and a contact of said control relay closed when the contacts of said relay are in their first position for supplying energy to the winding of said second auxiliary relay, a circuit including aback contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay, a back contact of the second auxiliary relay, and a contact of said control relay which is closed when the contacts of said relay are in their first position over which steady energy may be supplied to the rails of said rearward section, and means effective when the contacts of said control relay are in their second position to supply coded energy to the rails of said rearward section.

9. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow acting control relay having contacts movable between a first and a second position, the circuit of said control relay being governed by said auxiliary relays in such manner that when the contacts of both of said relays are-released the contacts of said control relay occupy their first position and so that when the contacts of the first relay are picked up while the contacts of the second auxiliary relay are released the contacts of said control relay7 move to their second position after a time-interval, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including aback contact of the track relay, a front contact of the first auxiliary relay and a contact of said control relay closed when the contacts of said relay are in their first position for supplying energy to the winding of said second auxiliary relay, a circuit including a back contact of the second auxiliary relay for supplying coded energy to the rails of said rearward section, a circuit including a, front contact of the iirst auxiliary relay, a back contact of the second auxiliary relay and a contact of said control relay which is closed when the contacts of said relay are in their first position over which steady energy may be supplied to the rails of said rearward section, and means responsive to back contact of the track relay, a front contact l of the first auxiliary relay and a contact of said control relay closed when the contacts of said relay are in their first position for supplying energy to the winding of saidsecond auxiliary i relay, a circuit including back contacts of said first and second auxiliary relays and a contact of said control relay closed when the contacts of said control relay are in their first position for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the iirst auxiliary relay, a back contact of the second auxiliary relay and a contact of said control relay closed when the contacts of said relay are in their first position over which steady energy may be supplied to the rails of said rearward section, a circuit including a contact of said control relay closed when the contacts of said relay are in their second position for supplying coded energy to the rails of said rearward section, and means responsive to continued code following operation of said track vrelay subsequent to picking up of the contacts of said first auxiliary relay for also supplying coded energy to the rails of said rearward section.

10. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a Winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow acting control relay having contacts movable between a rst and a second position, the circuit of said control relay being `governed by said auxiliary relays in such manner that when the contacts of both of said relays are released the contacts of said control relay occupy their first position and so that when the contacts of the first relay are picked up while the contacts of the second auxiliary relay are released the contacts of said control relay move to their second position after a time interval, a circuit including a front contact of continued code following operation of said track relay subsequent to picking up of the contacts of said first auxiliary relay for also supplying coded energy to the rails of said rearward section.

11. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow acting control relay having contacts movable between a first and a second position, the circuit of said control relay being governed by said auxiliaryv relays in such manner that when the contacts of both of said relays are released the contacts of said control relay occupy their first position and so that whenA the contacts of the first relay are picked up while the contacts of the second auxiliary relay are released the contacts of said control relay move to their second position after a time interval, a circuit including a front contact of the track r-elay for supplying energy to Vthe winding of the first auxiliary relay, a circuit including a contact of said control relay which is closedlwhen the contacts of said control relay are in their second position for also supplying energy to the first auxiliary relay, a circuit including a back contact of the track relay, a front contact of the first auxiliary relay and a contact `of said control relay closed when the contacts of said relay are in their first `position for supplying energy to the winding of said second auxiliary relay, a circuit including a back contact of one of saidauxiliary relays for 'supplying coded energy to the rails of said rearwardsection, a circuit including a front contact of the iirst auxiliary relay, a back contact of the sec- Vond auxiliary relay, and a Contact of said con- 12. In a coded railwayV signaling system, in

combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a first and a second auxiliary relay, a slow acting control relay having contacts movable between a first and a second position, the circuit of said control relay being governed by said auxiliary relays in such manner that when the contacts of both of said relays are released the `contacts of said control relay occupy their first position and so that when the contacts of the first relay pick up while the contacts of the second auxiliary relay are released the contacts of said control relay move to their second position after a time interval, a circuit including a front contact of the track relay for supplying energy to the winding of the first auxiliary relay, a circuit including a contact of said control relay which is closed when the contacts of said control relay are in their second position for alsosupplying energy to the first auxiliary relay, a circuit including a back contact of the track relay, a front Contact of the .first auxiliary relay and a contact of said control relay closed when the contacts of said relay are in their first position for supplying energy to the winding of said second auxiliary relay, a circuit including a back contact of one of said auxiliary relays for supplying coded energy to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay, a back contact of the second auxiliary relay, a contact of said control relay which is closed when the contacts of said relay are in their rst position over which steady energy may be supplied to the rails of said rearward section, means responsive to continued code following operation of the track relay subsequent to picking up of the contacts of said first auxiliary relay for also supplying coded energy to the rails of said rearward section, and manually operable means for interrupting the circuit of said first auxiliary relay.

13. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections including a forward and a rearward section, means for supplying coded energy to the rails of said forward section, a code following track relay having a winding receiving energy over the rails of said forward section, a circuit including a front contact of the track relay for supplying energy to a rst auxiliary relay, a circuit including a back contact of the track relay and a front contact of said rst auxiliary relay for supplying energy to a second auxiliary relay, a circuit including a back contact of one of lsaid auxiliary relays for supplying coded energy of a first code frequency to the rails of said rearward section, a circuit including a front contact of the first auxiliary relay and a back contact of the second auxiliary relay over which steady energy may be supplied to the rails of said rearward section, means responsive to continued code following operation of the track relay subsequent to picking up of the second auxiliary. relay for supplying energy of a second code frequency to the rails of said rearward section, and a control relay governed by contacts of the first and sec.

ond auxiliary relays in such manner that when the contacts of the auxiliary relays are out of correspondence the contacts of the control relay move to a position in which a contact of the control relay interrupts the circuit over which steady energy may be supplied to the rails of said rearward section and in which the control relay governs the supply of energy to the control relay to maintain the contacts of the relay in such position.

14. In a coded railway signaling system, in combination, a stretch of railway track having a pair of track rails divided by insulated joints into a plurality of successive track sections in cluding a forward and a rearward section, a code following track relay having a winding receiving energy over the rails of said forward section, a circuit over which coded energy of a first code frequency is supplied to the rails of said rearward section when said track relay is not responding to coded energy, means effective on initial picking up of the track relay contacts 'following a period in which the track relay has not been responding to coded energy to establish a circuit over which steady energy may be supplied to the rails of said rearward section, means responsive to continued code following operation of the track relay subsequent to initial picking up of the track relay contacts to interrupt the circuit over which steady energy may be supplied to the rails of said rearward section and to establish a circuit to supply coded energy of a second code frequency to the rails of said rearward section, a control relay effective when released to interrupt said circuit over which steady energy may be supplied to the rails oi said rearward section, and to prevent the supply of coded energy of said second code frequency to the rails of said rearward section, and means HOWARD A. THOMPSON. 

